Residual effects of lime and phosphorus applications on soil and maize (Zea mays L.) performance in a Kenyan highlands acid soil

In acid and phosphorus (P) deficient soils, lime and P-fertilizers increases crop yields. Residual effects of lime and Pfertilizer on soil pH, P availability, nutrient utilizations and maize yields was conducted at Kuinet (0 35’N & 35 18’E), Kenya. Treatments were: lime (0, 2, 4 and 6 tons/ha) containing 21% calcium oxide and P-fertilizer (0, 26 and 52 kg/ha), applied once in the year 2005 to monitor residual effects up to 2007. Each treatment received 75 kg N/ha except control. Kuinet soil was acidic (pH 4.8 & 39.4% aluminum), low in P (4.4 mg P/kg soil) and nitrogen (0.23%). Maintaining soil pH ≥ 5.5 with 2 tons lime required reapplication every 2 years, while maintaining soil P ≥10 mg P/kg soil required reapplication every one and three years for the 26 & 52 kg P/ha, respectively. Lime increased grain yield increased by 10, 31and 28% for 2, 4, 6 tons lime/ha and P fertilizer by 28 and 44% for 26 and 52 kg P/ha, respectively. Correlations between soil pH & P availability was poor (R = 0.142), while between soil available P & grain yield was weak (R = 0.341). Grain yield increased with soil P availability up to about 20 mg P/kg and thereafter the yield remained almost constant. Correlation between grain P & yield (R = 0.829) was highly significant (p ≤ 0.001). Soil acidity, N and P deficiencies limit maize production in Kuinet and similar soils in Kenyan highlands.